Emerald Ash Borer

adult ash borer

What It Is

Emerald Ash Borer (EAB) Agrilus planipennis is a destructive non-native beetle that feeds under the bark of ash trees and eventually kills them.

Where It Has Been Found

Originally from Asia, EAB was discovered in Michigan in 2002 and has been found in 29 states. It is estimated that it has killed over 60 million trees.

EAB was first found in Colorado in 2013 in the city of Boulder. Since then it has also been found in Gunbarrel, Lafayette, and Longmont.  It has not been found in Jefferson County.

USDA has established quarantine areas. Ash wood, trees or seedlings from the infested areas may not be brought into Jefferson County.  

Potential Impacts

Ash trees account for approximately 35% of the trees in our urban forests.  When we lose our trees to pests, we also lose the many environmental benefits trees bring to our neighborhoods.  

Environmental Benefits of Urban Trees

  • Capture rainfall and reduce runoff
  • Shade provides cooling and reduces energy use
  • Provide diversity for insects and wildlife

Building Resiliency in Urban Forests

Homeowners can contribute to the health of our urban forests by planting a variety of trees.  Having a mix of species reduces the impacts of pests like EAB that feed on a very limited host range.

List of Alternatives to Ash 


EAB Identification

EAB is a green metallic beetle that is about 1/2-3/4 inch long and 1/8 inch wide. The adult beetles emerge from the trunk and branches of the ash tree in May- early June through "D" shaped holes.  Adults feed on the trees' foliage and live 2-3 weeks.

The larva (immature stage) are white, segmented with a dark head.  They feed in S-shaped galleries under the bark.

View Lifecycle

Additional Information

Colorado Department of Agriculture - Emerald Ash Borer website

Ash Tree ID - Michigan

CSFS EAB Info

EAB Decision Guide

EAB Frequently Asked Questions - CSU

Emerald Ash Borer Information Network

ISA - Arborists

The North Central IPM Center Treatment Option Guide